In a motor driving control apparatus shown in FIG. 13 which has been known heretofore, a microcomputer 1 determines a command value Iq1* of motor drive current in dependence on a driving state, and in dependence on the command value Iq1*, an inverter control circuit 2 performs ON/OFF controls of respective switches UH, UL, VH, VL, WH, WL of a three-phase bridge circuit 3, whereby three-phase alternating currents as motor drive current are applied from the three-phase bridge circuit 3 to a three-phase brushless motor 4 for steering assist. Further, shunt resistances R1, R2, R3 are connected in series to the switches UL, VL, WL at a lower stage of the three-phase bridge circuit 3, and current-feedback control is performed by detecting an actual motor drive current based on inter-terminal voltages of these shunt resistances R1, R2, R3.
Patent Document 1: Japanese unexamined, published patent application No. 2004-117070 (FIG. 1)